I have a 1970 Donzi ski sporter 16 that came with a set of Holman Moody Manifolds to put on it. The previous owner said they were supposed to be the originals. They bolt right up to my Holman Moody 302 that is in the boat but the risers are definitely wrong for my application. They angle straight down and there is no chance of me being able to make any kind of bends to bring them around and connect them to the current exhaust ports in the hull there is just no space.

Really all I need is if I unbolt the riser section and just run the pipe straight out it will perfectly meet up with the current exhaust ports in my hull.

The boat will never sit in the water so I'm not concerned with not having a riser section but I'm not sure where I can find the part I need if anyone can guide me.

mattyboy

07-19-2016, 01:21 PM

You are looking for the snails. They made two versions one was an end dump which came straight out the back and the they made a down dump which were angled down the angled down work in a true inboard or with wide low thru hulls I would imagine the thru hulls on your 70 are narrow and high

mattyboy

07-19-2016, 01:28 PM

I think Holman Moody used glenwood marine exhaust with their logo on them

Look thru their catalog should have what you need

Make sure the old exhausts are in good shape don't want to ruin the motor
It may also pay to look at new center risers

http://www.glenwoodmarine.net/Catalog/EXHAUST%20SYSTEM.pdf

mattyboy

07-19-2016, 01:46 PM

You need a riser of some sort the riser protects the engine from internal cooling water not the outside lake water the flapper protects you from that
The riser mixes exhaust gas and Cooling water as far from the motor as possible to prevent reversion
resonance reversion is what will destroy your engine

70donzi16

07-19-2016, 03:01 PM

That glen wood link is great I will call them today and hopefully they will have what I need.

The H&M exhaust I am putting on the boat is NOS so it's new and in great shape. I think that glen wood straight water cooled outlet will work for my application.

Thank you again as always guys this site has been amazing help versus any other Google Search so far you guys are 2-0.

jl1962

07-19-2016, 06:26 PM

Thank you again as always guys this site has been amazing help versus any other Google Search so far you guys are 2-0.

Matty knows all............

woobs

07-20-2016, 09:46 AM

I found these HM manifolds last year.... They are around but, you have to look and be patient. FWIW, they were not expensive either.

woobs

07-20-2016, 10:05 AM

The other "almost" straight version look like this (pic below) and are for inboard engines.

woobs

07-20-2016, 10:19 AM

While the p/o of your boat said that HM manifolds were original on Donzi 16's , perhaps they were not original on "your" Donzi 16. They are very cool and imho worth the effort to fit.

However, you wouldn't be the first person to need to re-locate the through-hull exit tips. If you can't fit what you have and need to drill new holes there are covers/plugs that are made to cover the old holes if you don't want to glass/paint/repair the area. Maybe not the optimal solution but, an optional solution nevertheless.

http://www.cpperformance.com/p-345-transom-cover-plates.aspx

mattyboy

07-21-2016, 11:43 AM

My 16 had the snails like you are looking for they basically come straight back with a slight down angle after the hump in the riser I had about 3 inches of exhaust hose between the end of the riser and the thru hull fitting the end of the riser and the thru hull fitting almost touch like an inch apart